Enhanced fibrinolysis in fingerstick blood samples: a possible role for matrix metalloproteinase-9.

Our understanding of fibrinolysis is largely based upon analysis of blood drawn by venipuncture directly out of the intraluminal space without exposure to extravascular tissue [1]. However, physiologic fibrinolysis occurs predominantly extravascularly, as part of the global process of wound healing, and might involve mechanisms not operative in intravascular thrombolysis. To test the hypothesis that clots of extravasated blood lyse differently from clots of intravascular blood, we have compared fibrinolysis in fingerstick (FS) blood samples (which have briefly passed through extravascular tissue) with fibrinolysis in blood drawn by atraumatic venipuncture (VP) (which has avoided exposure to extravascular tissue). Our observations support a role for matrix metalloprotease-9 (MMP-9) in extravascular fibrinolysis [2,3].